Monitoring Rare Arctic-Alpine Plants at the Periphery of their Range in Glacier National Park, Montana: 2019 Report

Lesica, Peter

There is widespread agreement that increasing levels of atmospheric carbon dioxide and other greenhouse gases will result in global warming and widespread alteration of rainfall patterns during the next 50 years (Peters 1988, Henderson-Sellers 1990, IPCC 2007). The effects of these rapid climatic changes on the biota cannot be predicted; however, comparable but less rapid changes that occurred during the Pleistocene altered the ranges of many species (Webb 1992, Graham and Grimm 1990). High latitude floras are of relatively recent origin and are thought to provide a more sensitive indicator of climate change (Spicer and Chapman 1990). At equilibrium, the range of an organism is determined by its tolerance to stress in areas where environmental factors become limiting. Consequently species will be most sensitive to environmental change at the periphery of their range (Cain 1944, Parsons 1990). For these reasons arctic-alpine species at the southern limit of their range should be among the most sensitive indicators of the effects of global warming. Many arctic-alpine plants are at or near the southern limit of their range in Glacier National Park, Montana (Lesica et al. 1984). Among these are seven species of vascular plants that occur in wet tundra above timberline in the area around Logan Pass. These species and their tundra communities should be a sensitive bioassay of the changes in regional climate predicted to occur during the next 50 years. Monitoring this system will provide information on how different members of these communities respond to climate-induced stress. Baseline monitoring of these alpine communities and the peripherally rare species they support was conducted in 1988-91 (Lesica and McCune 1992, Lesica and Steele 1996), 2000-2002 (Lesica and McCune 2002, 2004), and 2010-2012. A fourth set of three consecutive years was begun in 2018. This report summarizes preliminary results for 2018-2019, the first two years of this fourth round of monitoring.